For automating the trawl line fishing, such automation being made necessary by the present speeds for running out and hauling aboard or turning the trawl line, baiting machines have been proposed, such as that disclosed in French Pat. No. 2,545,322 dated May 4, 1983, which fix the bait to the fish hook at the moment of the paying out of the line, and fish unhooking machines such as that disclosed in French Pat. No. 2,545,323 dated May 4, 1983, which remove the fish and the remaining bait from the fish hook while the main line is hauled in by a barring gear and store the trawl line in a storage magazine, the line being hung by its hooks suspended from a rail. The baiting machine takes over the trawl line from the magazine. If it is easy to detect fish hooks the leader of which has been cut by the trimming machine and those broken at the base of the shank because their leaders hang down underneath the line, it is impossible to detect the fish hooks which are opened or deformed because the fish hooks defile at a cadence which can reach 2000 hooks per hour.
Moreover, for certain types of fishing and for avoiding that the baits lie on the sea-bed, the trawl line is provided with floats and sinkers, generally a few chain links, which are alternately interposed between the fish hooks and fixed to the main line by leaders.